Field of the Invention
The present invention relates to the field of Lithium ion batteries.
Related Art
Rechargeable lithium-ion batteries hold great promise as energy storage devices to solve the temporal and geographical mismatch between the supply and demand of electricity, and are therefore critical for many applications such as portable electronics and electric vehicles. Electrodes in these batteries are based on intercalation reactions in which Li+ ions are inserted (extracted) from an open host structure with electron injection (removal). However, the current electrode materials have limited specific charge storage capacity and cannot achieve the higher energy density, higher power density, and longer lifespan that all these important applications require. Si as an alloying electrode material is attracting much attention because it has the highest known theoretical charge capacity (4200 mA h g−1). However, it is challenging to overcome the issues associated with alloying and conversion reactions, which involve large structure and volume changes (400% volume expansion for Si) during Li+ ion insertion and extraction. These issues can cause large hysteresis in the charge and discharge potentials, low power rate, and short cycle life, due to material instability, and poor electron and ion conduction.
Recently, Si nanostructures have been intensively explored to attack the volume expansion and fracture problem. For example, many Si nanostructures, such as Si nanowires, carbon/Si spheres, Si nanotubes, core-shell crystalline/amorphous Si nanowires, Si nanotubes, have also shown initial capacity close to the theoretical limit, good (>90%) capacity retention over a large number of cycles. However, low cost and fast throughput processes with great mass and morphology control are still desirable to reach the full potential for commercialization.